water level sensor testing - itrc · water level sensor testing itrc report no. 04-005 prepared by...
Post on 02-Jul-2018
215 Views
Preview:
TRANSCRIPT
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
IRRIGATION
TRAINING AND
RESEARCH
CENTER
Water Level Sensor Testing
November 2002/ December 2003
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Prepared by Dr. Stuart Styles Sarah Herman Marcus Yasutake Chuck Keezer Irrigation Training and Research Center (ITRC) California Polytechnic State University San Luis Obispo, CA 93407-0730 805-756-2429 www.itrc.org
Prepared for Bryce White Water Conservation Office Mid-Pacific Region United States Bureau of Reclamation Sacramento, California
Disclaimer: Reference to any specific process, product or service by manufacturer, trade name, trademark or otherwise does not necessarily imply endorsement or recommendation of use by either California Polytechnic State University, the Irrigation Training and Research Center, or any other party mentioned in this document. No party makes any warranty, express or implied and assumes no legal liability or responsibility for the accuracy or completeness of any apparatus, product, process or data described previously. This report was prepared by ITRC as an account of work done to date. All designs and cost estimates are subject to final confirmation.
Irrigation Training and Research Center December 2003
IRRIGATION
TRAINING AND
RESEARCH
CENTER
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -i-
EXECUTIVE SUMMARY
The findings presented here are the continuation of a series of studies begun in 1998 by the Irrigation Training and Research Center (ITRC) at California Polytechnic State University (Cal Poly), San Luis Obispo, California, on behalf of the Mid-Pacific Region of the United States Bureau of Reclamation (USBR) to test water level sensors under a variety of hydraulic conditions. This report is intended as a supplement to the original 1999 report, entitled “Water Level Sensor and Datalogger Testing and Demonstration” (ITRC Report No. R-01-010), which describes the testing processes in detail and presents detailed results for the first 17 sensors tested. The 1999 report can be accessed through the ITRC website (www.itrc.org). The 2003 research, summarized in this report, includes the testing of five new sensors. The goals for the original project were to determine the best way to monitor water level, and to develop a fast method for appraising sensors considered for irrigation district applications. This research addresses the need for water level sensors that are relatively simple to use and are very accurate over a broad range of hydraulic conditions. The use of water level sensor technologies, including ultrasonic sensors, pressure transducers, bubblers, and float sensors, was investigated for applications in a range of canals, reservoirs, and stilling wells. The testing results have been summarized with decision flow charts and rating tables for cross comparison. During laboratory testing conducted at the Cal Poly Water Delivery Facility, the water level sensors were installed in a portable monitoring demonstration unit built by ITRC. The sensors were tested under different hydraulic conditions and the data gathered was used to evaluate the performance of each of the water level sensors. The characteristics evaluated included long-term trending, time lag, output stability, linearity and hysteresis, drying effects, and the effects of air temperature.
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -ii-
TABLE OF CONTENTS
Executive Summary ........................................................................................................... i
Introduction ........................................................................................................................1
Background .....................................................................................................................1
Methodology .......................................................................................................................2
Equipment Setup .............................................................................................................2 Sensor Testing .................................................................................................................3
Long-term Trending ......................................................................................................... 3 Temperature Effects ......................................................................................................... 3 Linearity and Hysteresis .................................................................................................. 4 Time Lag .......................................................................................................................... 4 Output Stability ................................................................................................................ 4 Drying Effects .................................................................................................................. 4
Test Results .........................................................................................................................5 Selecting a Sensor ............................................................................................................ 5
Ultrasonic Sensors ...........................................................................................................6 Float Sensors ...................................................................................................................8
Celesco PT1MA Float Sensor ........................................................................................ 11 Submersible Sensors .....................................................................................................13
Druck PTX 1230/1830 ................................................................................................... 17 Keller 46W Pressure Transducer ................................................................................... 18 Stevens PS600 Pressure Transducer .............................................................................. 20 Endress+Hauser Waterpilot FMX 167 Pressure Transducer ....................................... 22
Bubbler Sensors ............................................................................................................25 BelTech BTS Bubbler ..................................................................................................... 28
Summary and Conclusions..............................................................................................31
References .........................................................................................................................32
Appendix A. Contact Information
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -iii-
LIST OF FIGURES
Figure 1. Photo of water level testing setup .......................................................................................... 2 Figure 2. Water level sensor selection guide ......................................................................................... 5 Figure 3. Flow chart for selecting an ultrasonic sensor ......................................................................... 6 Figure 4. Two basic float sensor models ............................................................................................... 8 Figure 5. Float sensor selection guide ................................................................................................... 9 Figure 6. Celesco PT1MA ................................................................................................................... 11 Figure 7. Celesco PT1MA temperature test results ............................................................................. 12 Figure 8. Celesco PT1MA long-term test ............................................................................................ 12 Figure 9. Celesco PT1MA drying test results ...................................................................................... 12 Figure 10. Celesco PT1MA output stability test results ...................................................................... 12 Figure 11. Basic submersible pressure sensor layouts ........................................................................ 13 Figure 12. Submersible pressure transmitter selection guide .............................................................. 15 Figure 13. Druck PTX 1230 (l.) and 1830 (r.) ..................................................................................... 17 Figure 14. Keller 46W ......................................................................................................................... 18 Figure 15. Keller 46W temperature test .............................................................................................. 19 Figure 16. Keller 46W long-term stability test .................................................................................... 19 Figure 17. Keller 46W drying test ....................................................................................................... 19 Figure 18. Keller 46W output stability test ......................................................................................... 19 Figure 19. Stevens PS600 .................................................................................................................... 20 Figure 20. Stevens temperature test results ......................................................................................... 21 Figure 21. Stevens long-term test results ............................................................................................ 21 Figure 22. Stevens drying test results .................................................................................................. 21 Figure 23. Stevens output stability test results .................................................................................... 21 Figure 24. Endress+Hauser Waterpilot FMX 167 ............................................................................... 22 Figure 25. Endress+Hauser FMX 167 temperature test ...................................................................... 24 Figure 26. Endress+Hauser FMX 167 long-term test .......................................................................... 24 Figure 27. Endress+Hauser FMX 167 drying test ............................................................................... 24 Figure 28. Endress+Hauser FMX 167 output stability test ................................................................. 24 Figure 29. Basic bubbler pressure sensor layouts ................................................................................ 25 Figure 30. Bubbler selection guide ...................................................................................................... 26 Figure 31. BelTech BTX Bubbler ....................................................................................................... 28 Figure 32. BelTech BTS temperature test ........................................................................................... 30 Figure 33. BelTech BTS long-term test .............................................................................................. 30 Figure 34. BelTech BTS drying test .................................................................................................... 30 Figure 35. BelTech BTS time lag test ................................................................................................. 30
LIST OF TABLES
Table 1. Evaluation results for all ultrasonic sensors tested by ITRC ................................................... 7 Table 2. Evaluation results for all float sensors tested by ITRC ......................................................... 10 Table 3. Evaluation ratings for Celesco PT1MA ................................................................................ 11 Table 4. Evaluation results for all submersible sensors tested by ITRC ............................................. 16 Table 5. Evaluation ratings for Keller 46W ........................................................................................ 18 Table 6. Evaluation ratings for Stevens PS600 ................................................................................... 20 Table 7. Evaluation ratings for Endress+Hauser FMX 167 ................................................................ 23 Table 8. Evaluation results for all bubbler sensors evaluated by ITRC .............................................. 27 Table 9. Evaluation ratings for BelTech BTS Bubbler ....................................................................... 29
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -1-
INTRODUCTION
Background The Irrigation Training and Research Center (ITRC) of California Polytechnic State University (Cal Poly), San Luis Obispo, was contracted on behalf of the USBR, Mid-Pacific Region to conduct research on water level measurement technologies that have potential applications in irrigation water distribution and delivery systems. ITRC began the first phase of this water level sensor study in 1999 by developing testing procedures and originally testing 17 water sensors. Since that time, additional sensors have been tested using the same procedures and the same equipment, in order to ensure comparable results with all tested products. This present report, which summarizes the findings of the more recent tests conducted at the Cal Poly Water Delivery Facility, was intended to be the first of several anticipated additions to the original study. Sensors tested for this project are those commonly used in irrigation applications:
ultrasonic sensors float sensors submersible pressure transducers bubbler sensors
As part of this study, ITRC has worked with selected manufacturers in the industry to obtain test units and evaluate their performances based on a standard set of specifications. The information and data contained in this report are being used to improve manufacturer specifications in order to increase the accuracy and reliability of the water level measurements provided by these devices, and to determine the feasibility, reliability and suitability of such technologies in their desired small-scale applications.
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -2-
METHODOLOGY
Equipment Setup A testing setup was developed by ITRC in order to create a standard for a continuous sensor evaluation project. The setup includes a portable SCADAPak, a computer with the appropriate software, a sensor testing tank, a holding tank, two pumps, and the appropriate sensors connected to the SCADAPak. This simple setup makes it possible for ITRC to easily and quickly conduct similar studies in the future. The format of the evaluation procedure also allows for other sensors and updates to be added to the series of testing.
Figure 1. Photo of water level testing setup In the testing procedure, two variables were monitored: the water level and the air temperature. Two sets of tests were performed. During the first set of tests, three new sensors monitored the water level: a Keller 46W pressure transducer, a BelTech BTS bubbler, and a Celesco PT1MA float. A Druck PTX 1230 water level sensor was used for control purposes during testing. The air temperature was monitored using three thermocouples. The second set of tests measured and compared two submersible pressure transducers: an Endress+Hauser Waterpilot FMX 167, and a Stevens PS600. During this test, the Druck PTX 1230 was used for the control, and a Druck PTX 1830 was run alongside the new sensors for comparison. The software program LOOKOUT was used to display all sensor test results. The program was set up to log data (results) to a CSV (comma separated variable) file in Excel, and was subsequently analyzed. For further information on the SCADA setup or LOOKOUT, refer to the ITRC reports “Remote Monitoring and Control” and “LOOKOUT Instructions for a Portable SCADA System.”
Computer
Holding Tank
Portable SCADAPak
Testing Tank
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -3-
Sensor Testing For this study, float sensors, submersible pressure sensors, and bubbler pressure sensors were tested. Several ultrasonic sensors were evaluated for the 1999 report, but no new sensors in that category were tested for this phase. All sensors were tested for mechanical characteristics such as power requirements, ease of installation, and simplicity of instructions. More importantly, the sensors were also tested for the following performance features:
Long-term trending (reliability) Air and water temperature effects
(performance during fluctuating temperatures)
Drying effects Output stability Time lag (water level response time) Linearity and hysteresis
Several other characteristics, such as foam penetration effects, wave damping, DC power requirement, and others, were used in the testing of sensors for the 1999 report, but are no longer considered because there was either little or no variation among the sensors, or it was found that those characteristics did not affect the sensors’ performance. Only those characteristics listed above were tested for the current report. Detailed explanations of characteristics and testing methods can be found in the 1999 ITRC report “Water Level Sensor and Datalogger Testing and Demonstration.” Below are brief descriptions of the features tested for the current research.
Long-term Trending
This test was set up to allow the pumps to maintain a high point setting and a low point setting for a certain amount of time. Three long-term stability tests were run so that the data could be compared. When all tests were complete the data was analyzed separately for each test and for each sensor, and graphs were developed. By examining and comparing the graphs it was possible to determine which sensors did well over long periods of time.
Temperature Effects
This test was set up to induce a change in the air temperature. A canvas tarp was used to cover the testing area, so that the heat would be focused towards the tank and the sensors. An electric (portable) heater was used to create heat under the tarp. On the first day of testing, the air temperature in the tank was raised and maintained for two hours. The enclosure was allowed to cool for two hours, and then heated again for two hours. Overnight, the temperature dropped to about 17 degrees Celsius. On the second day of testing, the air temperature was raised and maintained for six consecutive hours. Once testing was complete, a graph was developed for each sensor showing time (hours) versus water level (inches).
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -4-
Linearity and Hysteresis
For this test the sensors were tested at eight different water levels. At each water level, a settling time of two minutes was used. Ten readings were taken at each water level at a poll rate of once per second. Therefore, the pumps were only off for two minutes and ten seconds at each level. The true water level was read off a metric staff gauge and recorded for each data point. The data was then analyzed by plotting sensor output (in raw numbers) versus the actual water depth in inches. Hysteresis is the maximum difference in output, at any measured value within the specified range, when the value is approached first with increasing and then with decreasing measurements. Linearity is the closeness of a calibration curve to a specified straight line.
Time Lag
For this test, the water was raised for a set amount of time, maintained at that level for five minutes, and then dropped back down to its original level. Once the original level was maintained, the second pump was instantly turned on to repeat the cycle. Individual graphs were developed for each sensor showing time (seconds) versus water level (inches). The graphs made it possible to analyze time lag by looking at how well the sensor readings matched the actual water levels as the pumps were raising or lowering the water depth.
Output Stability
For this test, the water level of 18 inches was maintained in the test tank for two hours. A plot of the output from each sensor was analyzed for stability (how much it oscillated around the average reading). The graphs were set up to show time (minutes) versus water level (inches). An ideal sensor would show a straight line (throughout the test) at the water level set point.
Drying Effects
This test allowed the sensors to be dried out for a short period of time in order to determine how well they reacted to drying. Data was logged for two hours before the sensors were removed from the tank to dry for five days. After the drying period the sensors were placed back into the water and data was logged for two hours after the drying period. The data was analyzed by plotting the water level versus time to see how drying each sensor affected the accuracy of its readings.
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -5-
TEST RESULTS
Selecting a Sensor
Each of the sensors was rated on a scale from one to ten, based on the performance of all sensors, (one being the worst and ten being the best). The sensors were also rated on the ease of installation and calibration, each individual performance test, and overall accuracy. The flow chart below was developed to assist in the selection of a sensor type for various applications.
Figure 2. Water level sensor selection guide
Water Level Sensor Testing http://www.itrc.org/reports/pdf/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -6-
Ultrasonic Sensors General. Ultrasonic sensors transmit a series of cone-shaped sound waves through the air. These sound pulses reflect off the liquid surface and are in turn received by the sensor, which measures the time interval between the transmitted and received signal. Electronics then convert this time interval into a distance measurement using the speed of sound in air. No part of the sensor ever touches the water – a distinct advantage of this sensor type.
General Advantages
- Non-contacting, so are not affected by dirty water, floating debris, or aquatic wildlife
- Not affected by fluctuating water temperatures
- Not affected by high flow rates - Easy to calibrate - Low maintenance - Excellent linearity and lack of
significant hysteresis - Can withstand freezing temperatures - Long-term reliability
General Disadvantages
- Affected by air temperature fluctuations - May reflect off floating foam or debris - Must be aligned precisely - May be affected by turbulent water (a stilling
well may be required) - May display misleading readings if echo is lost - Large beam angles cannot be used in
constricted spaces - Some sensors damaged by flooding (i.e., they
are not waterproof) - Some delay between the time when power is
first applied and the first output
Figure 3. Flow chart for selecting an ultrasonic sensor
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -7-
Evaluation results for all ultrasonic sensors tested by ITRC are found below. No new ultrasonic sensors have come on the market, so there have been no ultrasonic sensors tested by ITRC since the 1999 report.
Table 1. Evaluation results for all ultrasonic sensors tested by ITRC S
enso
r B
rand
Sen
sor
Mod
el
Sim
plic
ity a
nd C
orre
ctne
ss o
f In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Wat
er L
evel
Dis
play
?
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wav
e D
ampi
ng
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
List
Pri
ce
Ove
rall
Rat
ing
ULTRASONIC SENSORS
Badger 2500 9 8 9 10 Yes 3 10 10 10 10 A** 10 8 5 10 7 10 $1,600 8
Bailey-Fischer & Porter
50US3000
7 8 7 10 Opt. 4 10 2 10 10 9 10 7 10 10 AC only
10 $1,900 7
Endress + Hauser
Prosonic T FMU
230 5 8 5 10 Opt. 2 10 2 10 10 A** 10 8 6 10 9 10 $585 7
Lundahl DCU-7110
10 8 9 10 On
Lap-top
1 10 1 10 10 1 10 7 8 10 7 10 $615 7
Miltronics The
Probe 9 9 9 10 Yes 2 10 5 10 10 A** 10 2 8 10 9 NA $695 8
* Error may have been introduced in the RS-232C to 4-20 MA output conversion. ** Increasing the wave damping effect will decrease the water level response time. 10 = excellent; 1 = horrible; NA = not available; A = adjustable, SW = stilling well required; SW? = stilling well recommended; Opt. = optional
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -8-
Float Sensors General. There are two basic types of float sensor, one which involves a pulley and counterweight and one which utilizes a spring to produce an upward force on the float cable.
Figure 4. Two basic float sensor models In the pulley and counterweight version, a counterweight provides tension to a beaded cable. Notches in the pulley mesh with cable beads, forcing the pulley to turn as the water level rises or lowers and the float goes up or down. This version of the float sensor is the more difficult to install and calibrate. The pulley has a “travel stop” for both the clockwise and counterclockwise directions. During installation, the user must ensure that neither travel stop will be hit between the highest and lowest expected positions. Additionally, the float must be placed on the correct side of the pulley. In the second model, the cable wraps and unwraps around a spring-loaded shaft inside the sensor. To install, simply hook a float to the cable and lower it to the water. If the distance between the highest expected water level and the sensor is more than about 20 cm, extra cable should be installed between the standard sensor cable and the float instead of purchasing a longer-range sensor. This will ensure the highest possible resolution across the measurement range. Turns of the pulley or spring-loaded shaft change the resistance of a potentiometer within the sensor housing, changing the output electrical voltage or current. Though the electronics are less complex than in an ultrasonic sensor, they still must be mounted directly over the water. If the water level fluctuates around a certain level for an extended period of time (dithering), the potentiometer may wear out quickly.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -9-
General Advantages
- Not affected by dirty water - Not affected by water temperature - Not affected by foam - Low effect of changing air temperatures - Low maintenance - Low cost - Can withstand freezing temperatures - No delay between the time when power
is first applied and the first output
General Disadvantages
- Stilling well required - Cable may slip (pulley and
counterweight type only) - Easily vandalized unless enclosed - May wear if water level remains at one
position for extended periods - Salt build-up may freeze the pulley - Some sensors damaged by flooding
The Celesco PT1MA was the only new float sensor tested. Therefore, it was the only new sensor incorporated into the selection guide below.
12” stilling well possible?
< $450 per sensor
desired?
Intermountain Environmental
G-FP10CCelesco PT1MA
Celesco PT420
Yes
Current (4-20 mA)
Voltage (0-4 V)
No
Why the PT420 is more expensive: 1. PT420 comes in an enclosed box 2. The cable tension on the PT420 can be adjusted 3. Electrical connections can vary
Float Sensor Selection Guide
Figure 5. Float sensor selection guide
Some of the differences between the two Celesco sensors (tested) are listed below the flow chart. The Celesco PT420 is typically used for gate movement and calibration. It is common to find a PT420 used in combination with a SCADA system. The PT1MA is used in several districts and other applications for flow studies because of its reliability and low cost.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -10-
Evaluation results for all float sensors tested by ITRC are found below. The new sensor tested for this report is listed in bold.
Table 2. Evaluation results for all float sensors tested by ITRC
Sen
sor
Bra
nd
Sen
sor
Mod
el
Sen
sor
Typ
e
Sim
plic
ity a
nd C
orre
ctne
ss o
f In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Wat
er L
evel
Dis
play
?
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wav
e D
ampi
ng
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
List
Pri
ce
Ove
rall
Rat
ing
FLOAT SENSORS
Celesco PT420
PT420 Float 10 7 10 10 No 9 10 10 10 10 SW 10 9 10 10 9 NA $485 10
Intermountain Environmental
G-FP10C Float & Pulley
10 6 8 10 No 7 10 10 10 10 SW 10 8 9 10 10 10 $350 9
Celesco PT1MA
PT1MA Float NA 9 8 - No 6 - - - - - 10 10 10 8 - 9 $389 9
* Error may have been introduced in the RS-232C to 4-20 MA output conversion. ** Increasing the wave damping effect will decrease the water level response time. 10 = excellent; 1 = horrible; NA = not available; A = adjustable, SW = stilling well required; SW? = stilling well recommended; Opt. = optional
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -11-
Celesco PT1MA Float Sensor
(800) 423-5483 http://www.celesco.com General. The PT1MA adds a 4 – 20 mA position feedback signal to Celesco’s compact line of cable-extension transducers. The PT1MA is available with full stroke ranges from as little as 2 inches up to 50 inches with adjustable zero and span settings to precisely match the full scale output to your exact measurement range. The PT1MA offers several options including forward and reverse 0–20 and 4–20 mA output signals, alternate measuring cable exits and a couple of different electrical connection options.
Photo obtained at www.intertechnology.com
Figure 6. Celesco PT1MA Test Results: The Celesco PT1MA rated well when compared to other float sensors. The overall rating on a scale from one to ten was a nine (Table 3). The sensor produced accurate readings when the water level was held constant for a period of time as well as when the water level was continuously changing. It earned its lowest rating (a 6) during the air temperature test. As shown in Figure 7, when the air temperature rose, the sensor’s reading dipped slightly. However, the Celesco PT1MA did well in its other areas. There were a few jumps in the water level during the output stability test reading (Figure 9) due to the resolution of the sensor, but other than those jumps, the graph showed a straight line at a constant water level.
Table 3. Evaluation ratings for Celesco PT1MA
Sen
sor
Bra
nd a
nd
Mod
el
Sim
plic
ity a
nd
Cor
rect
ness
of
Inst
ruct
ions
Eas
e of
Ins
talla
tion
Eas
e of
Cal
ibra
tion
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Wat
er L
evel
R
esp
onse
Tim
e
Lin
earit
y an
d H
yste
resi
s
Out
put S
tabi
lity
Abi
lity
to R
ead
Q
uick
ly A
fter
Ext
ende
d D
ry P
erio
d
Lon
g T
erm
Rel
iabi
lity
Ove
rall
Rat
ing
Celesco PT1MA
NA 9 8 6 10 10 10 8 9 9
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -12-
Air Temperature Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00
Time (hours)
Se
nso
r O
utp
ut
(in
ches
)
0
10
20
30
40
50
60
Air
Tem
per
atu
re (
C)
Celesco
Air Temperature
Figure 7. Celesco PT1MA temperature test results
Long Term Trending
10
11
12
13
14
15
16
17
18
19
20
8/9/20020:00
8/9/200212:00
8/10/20020:00
8/10/200212:00
8/11/20020:00
8/11/200212:00
8/12/20020:00
8/12/200212:00
8/13/20020:00
Time
Dep
th (
inch
es)
Druck (control)
Celesco
Figure 8. Celesco PT1MA long-term test
Celesco Drying Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0 50 100 150 200 250 300 350 400
Time (minutes)
Wa
ter
Le
ve
l (i
nc
he
s)
Celesco
Druck (control)Dry for 5 days
Figure 9. Celesco PT1MA drying test results
Output Stability
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
8/15/20028:09
8/15/20028:24
8/15/20028:38
8/15/20028:52
8/15/20029:07
8/15/20029:21
8/15/20029:36
8/15/20029:50
8/15/200210:04
8/15/200210:19
8/15/200210:33
Time
Dep
th (
inch
es)
Druck (control)
Celesco
Figure 10. Celesco PT1MA output stability test results
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -13-
Submersible Sensors General. At any given level, both liquids and gasses exert an equal pressure in all directions. Water pressure increases linearly with depth of submergence. For every 70 cm (2.31 ft) of water, pressure increases by 1 PSI. The pressure difference between the atmosphere and the water around the sensor head produces a force on a flexible diaphragm. Electronics convert the force on the diaphragm into a proportional electric signal. All submersible pressure sensors studied had a standard or optional 4 – 20 mA output signal.
Figure 11. Basic submersible pressure sensor layouts The vent tube is an important component in submersible pressure transducer. Transducers measure the water and air pressure combined, and without a vent tube, the sensors cannot distinguish between a change in water pressure caused by water level, and changes in barometric pressure. For this study, all pressure sensors were equipped with vent tubes, and hourly atmospheric data for San Luis Obispo was compared with data from the tests for all sensors. No correlation was found between the sensor results and barometric pressure changes during testing. Desiccant. The vent tube must remain dry, necessitating the use of a desiccant or bellows at the open end. Desiccant is a chemical that absorbs water vapor. Desiccants used with pressure sensors generally change color when in need of replacement. As an alternative to desiccant, bellows or an air bladder can separate the air within the vent tube from the atmosphere while allowing the pressures to equilibrate. Absolute pressure sensors do not have vent tubes and therefore require no desiccant and lower maintenance. However, some type of barometric sensor would be required to provide a reading to the datalogger or PLC, where the pressure sensor output can be corrected for changes in atmospheric pressure. Installation. A submersible pressure sensor is very easy to install—simply lower it into a stilling well so that the water intake ports are about 10 cm below the lowest water level that is of interest to monitor. To avoid damage to the sensor, do not place it where it could go deeper than the overpressure rating. An overpressure rating of 3x for a 0 – 3-m range sensor means that it will be damaged at depths greater than 9 m. If possible, install the sensor deep enough so that it will be below ice that may form on the surface. If the water could freeze around or inside the sensor, it must be removed from the water before any ice forms. A sensor can easily be crushed as water freezes around it.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -14-
When installing, lower the transducer slowly into the water. To avoid permanent damage to the diaphragm or electronics, do not drop the sensor or strike it against a hard object. Secure the cable so that it will not slip and change the depth of the sensor. Cable harnesses are available from some manufacturers. If the sensor is installed in a deep well, the large amount of cable may stretch over time due to its own weight. Druck includes a Kevlar cord inside the cable jacket to avoid stretching. Otherwise, some other type of support cable should be used.
General Advantages
- Easy to install - Electronics are hidden from view - Low power draw - Not usually affected by air temperature
fluctuations - Not affected by foam - Almost no time lag - No delay between the time when power
is first applied and the first output
General Disadvantages
- Damaged by ice - Can clog in dirty water - Susceptible to malfunction if often
allowed to dry - May hang up debris - Adversely affected by water temperature
fluctuations - Range is not adjustable - Desiccant must be periodically replaced - Stilling well often required - Lightning protection recommended - Damaged if submerged much too deep - Easily damaged by aquatic wildlife
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -15-
The Keller 46W, Endress+Hauser FMX 167, and Stevens PS600 have been incorporated into the selection guide.
Submersible pressure transmitter selection guide
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -16-
Among irrigation districts and farmers, the most widely used sensor for flow measurement studies is the Druck 1230 (0-1 psi range). Evaluation results for all submersible sensors tested by ITRC are found below. The new sensors tested for this report are listed in bold.
Table 4. Evaluation results for all submersible sensors tested by ITRC S
enso
r B
rand
Sen
sor
Mod
el
Sim
plic
ity a
nd C
orre
ctne
ss o
f In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Wat
er L
evel
Dis
play
?
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wav
e D
ampi
ng
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
List
Pri
ce
Ove
rall
Rat
ing
SUBMERSIBLE SENSORS
Automata LEVEL-WATCH
10 7 10 10 Opt. 7 3 10 1 1 SW? 10 2 9 1 9 7 $328 4
Global Water WL300 10 9 10 10 No 9 3 10 1 1 SW? 10 9 5 1 9 2 $495 5
Stevens PS600 10 9 10 10 No 10 10 10 9 1 SW? 10 8 9 7 9 8 $790 8
Endress + Hauser
FMX 167 10 9 10 10 No 10 10 10 9 1 SW? 10 8 9 7 9 8 $730 8
Druck PTX 1830
10 9 10 10 No 10 10 10 9 1 SW? 10 8 9 7 9 8 $685-$1135
8
Instrumentation Northwest
PS9800 10 9 10 10 No 10 5 10 9 1 SW? 10 8 9 10 9 7 $479 8
KPSI 210S 10 9 10 10 No 10 6 10 9 1 SW? 10 10 10 10 9 4 $778 8
Stevens SDT-II 10 7 10 10 No 10 5 10 9 1 SW? 10 8 9 NA 9 8 $707 8
Keller 46W Series 46 NA 9 9 - No 7 - - - - - 8 9 5 2 - 2 $495 6
* Error may have been introduced in the RS-232C to 4-20 MA output conversion. ** Increasing the wave damping effect will decrease the water level response time. 10 = excellent; 1 = horrible; NA = not available; A = adjustable, SW = stilling well required; SW? = stilling well recommended; Opt. = optional
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -17-
Druck PTX 1230/1830
(203) 746-0400 http://www.druck.com/usa General. For the current testing, a Druck PTX 1230 was used as the control sensor to measure the water level because of its proven reliability, as well as its excellent performance in the field and during earlier tests. Another sensor in the same series, the Druck PTX 1830, was tested for the 1999 report and performed well among the submersible pressure transducers, demonstrating especially impressive accuracy during fluctuating water temperatures. Because of its reliability, the PTX 1830 was tested alongside the new sensors in this phase as a standard against which the new sensors could be compared. The only difference between the PTX 1230 and 1830 is that the PTX 1230 is rated at ±0.25% full-scale accuracy, while the PTX 1830 is rated at ±0.1% full-scale accuracy.
Photos obtained at www.druck.com
Figure 13. Druck PTX 1230 (l.) and 1830 (r.)
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -18-
Keller 46W Pressure Transducer
(877) 2-KELLER http://www.Keller46W-Druck1230.com General. The Keller 46W submersible water level transducer is marketed for its rugged build and good linearity. The Kavlico low pressure capsule measures the pressure generated by the head of water above it, and is enclosed in a sealed stainless steel housing with the diaphragm protected by a gold layer. A neoprene O-ring seals the sensing diaphragm to the housing. The transmitter circuit is based on the Keller “Progres” ASIC, and can be reprogrammed by the user before or after installation (programmable version only).
Photo obtained from manufacturer’s website
Figure 14. Keller 46W Test Results: This sensor did not perform well, despite nearly perfect linearity and hysteresis results and very little variation in output due to increased air temperature (Figure 15). Over the series of tests the Keller 46W slowly began reading higher than the actual water level. This problem started approximately 280 hours (11.7 days) after calibration, during one of the long-term stability tests. The higher reading continued throughout the remainder of the testing, as shown in Figures 16 and 18. The high readings were apparent in the time lag and drying tests as well. After drying, the Keller 46W showed the same pattern as the long-term trending results. The readings started out at one level and slowly increased as time went on. The graph in Figure 17 shows the output from the sensor before and after the five-day drying period. Because of these progressively higher readings, the Keller proved to be unreliable over time.
Table 5. Evaluation ratings for Keller 46W
Sen
sor
Bra
nd a
nd
Mod
el
Sim
plic
ity a
nd
Cor
rect
ness
of
Inst
ruct
ions
Eas
e of
Ins
talla
tion
Eas
e of
Cal
ibra
tion
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Wat
er L
evel
Res
pons
e T
ime
Lin
earit
y an
d H
yste
resi
s
Out
put S
tabi
lity
Abi
lity
to R
ead
Qui
ckly
A
fter
Ext
ende
d D
ry
Per
iod
Lon
g T
erm
Rel
iabi
lity
Ove
rall
Rat
ing
Keller 46W NA 9 9 7 8 9 5 2 2 6
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -19-
Air Temperature Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00
Time (hours)
Sen
sor
Ou
tpu
t (i
nch
es)
0
10
20
30
40
50
60
Air
Tem
per
atu
re (
C)
Keller
Air Temperature
Figure 15. Keller 46W temperature test
Long Term Stability
10
11
12
13
14
15
16
17
18
19
20
0.00 6.00 12.00 18.00 24.00 30.00 36.00 42.00 48.00 54.00 60.00 66.00 72.00
Time (hours)
Act
ual
Wat
er L
evel
(in
ches
)
Druck (control)
Keller
Figure 16. Keller 46W long-term stability test
Keller Drying Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0 50 100 150 200 250 300 350 400
Time (minutes)
Wat
er
Le
ve
l (i
nc
he
s)
Keller
Druck (control)Dry for 5 days
Figure 17. Keller 46W drying test
Output Stability
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
8/15/20028:09
8/15/20028:24
8/15/20028:38
8/15/20028:52
8/15/20029:07
8/15/20029:21
8/15/20029:36
8/15/20029:50
8/15/200210:04
8/15/200210:19
8/15/200210:33
Time
Dep
th (
inch
es)
Druck (control)
Keller
Figure 18. Keller 46W output stability test
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -20-
Stevens PS600 Pressure Transducer
(800) 452-5272 http://www.stevenswater.com General: It is important to note that the PS600 is no longer being manufactured by Stevens. The approximate cost listed in the sensor comparison chart at the beginning of this section is for the PS700, which is the latest in the series. The PS700 has the same specifications and can be substituted for PS600.
Figure 19. Stevens PS600
Test Results: The results for this sensor demonstrated very good performance. Overall (among the submersible pressure transmitters) the Stevens PS600 rated an eight on a scale from one to ten. The sensor gave nearly perfect linearity and hysteresis results and showed very little variation in output due to increased air temperature. During nearly every test, the Stevens’ output matched the output of the Druck 1230 control sensor, as shown in Figures 20 through 23.
Table 6. Evaluation ratings for Stevens PS600
Sen
sor
Bra
nd a
nd
Mod
el
Sim
plic
ity a
nd C
orre
ctne
ss
of In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
Ove
rall
Rat
ing
Stevens PS600 10 9 10 10 10 10 10 9 1 10 8 9 7 9 8 8
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -21-
Temperature Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
13:26 13:40 13:55 14:09 14:24 14:38 14:52 15:07 15:21 15:36 15:50
Date & Time
Dep
th (
inch
es)
15
20
25
30
35
40
Tem
per
atu
re (
deg
rees
C)
Druck (control)
Stevens
Water Temperature
Figure 20. Stevens temperature test results
Long-Term Reliability
10
11
12
13
14
15
16
17
18
19
20
11/14/2003 0:00 11/14/2003 12:00 11/15/2003 0:00 11/15/2003 12:00 11/16/2003 0:00 11/16/2003 12:00 11/17/2003 0:00
Time
De
pth
(in
ch
es)
Druck (control)
Stevens
Figure 21. Stevens long-term test results
Stevens Dry Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0 50 100 150 200 250 300 350 400
Time (minutes)
Dep
th (
inch
es)
Druck (control)
Stevens
Figure 22. Stevens drying test results
Output Stability Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
11/21/2003 13:26
11/21/2003 13:40
11/21/2003 13:55
11/21/2003 14:09
11/21/2003 14:24
11/21/2003 14:38
11/21/2003 14:52
11/21/2003 15:07
11/21/2003 15:21
11/21/2003 15:36
11/21/2003 15:50
Time
De
pth
(in
ch
es
)
Druck (control)
Stevens
Figure 23. Stevens output stability test results
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -22-
Endress+Hauser Waterpilot FMX 167 Pressure Transducer
(888) ENDRESS http://www.us.endress.com
General: The Endress+Hauser Waterpilot FMX 167 pressure transducer is a submersible level transmitter with a ceramic pressure sensor for use in applications where coating and fouling can disable other submersible transducers. The Waterpilot is available with nine permanently calibrated measuring ranges from 3 to 600 ftH20 to ensure use in all standard applications (optional application specific range). Due to its compact outer diameter of only 0.87" (22mm), it is ideal for use in 1" well casings as well. As an option, a function permitting the simultaneous measurement of level and temperature is available (integrated temperature sensor Pt 100).
Figure 24. Endress+Hauser Waterpilot FMX 167
Benefits of the Waterpilot FMX 167 include permanent hermetically sealed cable probe, high mechanical resistance to overload and aggressive media, high-precision and long-term stability ceramic measuring cell, potted electronics and 2-filter pressure compensation system, which provide resistance to climatic changes. The FMX 167 has electronics comprising 4-20mA output signal and integrated overvoltage protection. Drinking water approvals include KTW, NSF, and (ACS in preparation). The sensor is certified to ATEX II 2 G/EEx ia, FM and CSA. Its rugged terminal housing (IP 66/IP 67) includes a GORE-TEX filter for pressure protection. Complete measuring point solutions are available through comprehensive accessories from Endress+Hauser. Test Results: Overall (among the submersible pressure transmitters) the Endress+Hauser Waterpilot FMX 167 gave nearly perfect linearity and hysteresis results and showed little variation in output due to increased air temperature, other than a slight dip in readings when the air temperature spiked. After drying, the output was slightly elevated and stayed at this level (Figure 27). This reading was slightly more pronounced than with the other pressure sensors tested; however, the difference was only about five hundredths of an inch. Therefore, its rating in the drying test is consistent with other similar pressure transmitters.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -23-
Table 7. Evaluation ratings for Endress+Hauser FMX 167
Sen
sor
Bra
nd a
nd
Mod
el
Sim
plic
ity a
nd C
orre
ctne
ss o
f In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
Ove
rall
Rat
ing
Endres Hauser Waterpilot FMX
167 10 9 10 10 10 10 10 9 1 10 8 9 7 9 8 8
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -24-
Temperature Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
13:26 13:40 13:55 14:09 14:24 14:38 14:52 15:07 15:21 15:36 15:50
Date & Time
Dep
th (
inch
es)
15
20
25
30
35
40
Tem
per
atu
re (
deg
rees
C)
Druck (control)
Endress Hauser
Water Temperature
Figure 25. Endress+Hauser FMX 167 temperature test
Long-Term Reliability
10
11
12
13
14
15
16
17
18
19
20
11/14/2003 0:00 11/14/2003 12:00 11/15/2003 0:00 11/15/2003 12:00 11/16/2003 0:00 11/16/2003 12:00 11/17/2003 0:00
Time
De
pth
(in
ch
es
)
Druck (control)
Endress+Hauser
Figure 26. Endress+Hauser FMX 167 long-term test
Endress+Hauser Dry Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0 50 100 150 200 250 300 350 400
Time (minutes)
Dep
th (
inch
es)
Druck (control)
Endress+Hauser
Figure 27. Endress+Hauser FMX 167 drying test
Output Stability Test
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
11/21/2003 13:26
11/21/2003 13:40
11/21/2003 13:55
11/21/2003 14:09
11/21/2003 14:24
11/21/2003 14:38
11/21/2003 14:52
11/21/2003 15:07
11/21/2003 15:21
11/21/2003 15:36
11/21/2003 15:50
Time
Dep
th (
inch
es)
Druck (control)
Endress+Hauser
Figure 28. Endress+Hauser FMX 167 output stability test
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -25-
Bubbler Sensors General. Bubblers measure water level by sensing the pressure of one or more air-filled tubes or chambers that have an open, submerged bottom end. The higher the water level and therefore the higher the static pressure at the end of the bubbler tube, the more air pressure is needed to fill the tube. Air is often continually bled out of each tube for three reasons: 1) to keep dirt and debris out of the line, 2) to lower the effect of a leak, and 3) to keep the air in the tube from dissolving in the water. The pressure in the tube minus atmospheric pressure is proportional to water level. Figure 29 shows the three basic layouts for bubbler pressure sensors.
Figure 29. Basic bubbler pressure sensor layouts Installation. Install the most shallow tube outlet about 15 cm below the lowest water level that is of interest to monitor. Bubbler lines must be securely installed to avoid any change in position of the submerged end. The tube may bend or curl over time, so secure it as close to the submerged end as possible. Some manufacturers provide a metal tube (which is connected to the end of the flexible plastic tubing) to help ease installation. Seal the plastic tubing around the metal with a hose clamp or piece of heavy-duty wire to avoid leaks. If a metal end-piece is not supplied, cut the submerged end at a 45 angle (except for a captive air system). Use as little tubing as needed, and run it downhill the entire way from the electronics to the submerged end if possible. This will help to keep water vapor condensation from accumulating in the line. Mount the electronics above the high water line—tubing can be run for long distances if required. Since any plastic tubing can crack if exposed to the sun too long, it should be run through PVC pipe or conduit in long-term installations.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -26-
General Advantages
- Easy to install and calibrate - Electronics can be installed away from
the water - Only inexpensive bubbler tubing
contacts the water - Not significantly affected by air or
water temperature fluctuations - Not significantly affected by drying - Not affected by foam - Not easily clogged by dirty water
General Disadvantages - May hang up debris - Requires one of the following:
1. A large nitrogen tank, which must be periodically refilled
2. A power-hungry air compressor with desiccant packs that must be periodically replaced
- High list price - Sensor output may lag behind a
changing water level
The BelTech BTS bubbler was incorporated into the flow chart below to assist in the selection of the appropriate sensor.
Figure 30. Bubbler selection guide
Several other differences exist between sensors that are not apparent in the flow charts above. With some further research, the differences can be determined and the perfect sensor for each application can be selected. Contact information for each of the sensors can be found in Appendix A of this report.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -27-
Evaluation results for all bubbler sensors tested by ITRC are found below. The new sensor tested for this report is listed in bold.
Table 8. Evaluation results for all bubbler sensors evaluated by ITRC
Sen
sor
Bra
nd
Sen
sor
Mod
el
Sen
sor
Typ
e
Sim
plic
ity a
nd C
orre
ctne
ss o
f In
stru
ctio
ns
Eas
e of
Inst
alla
tion
Eas
e of
Cal
ibra
tion
Com
patib
ility
with
Oth
er
Bra
nd D
atal
ogge
rs
Wat
er L
evel
Dis
play
?
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Per
form
ance
Dur
ing
Flu
ctua
ting
Wat
er
Tem
pera
ture
Foa
m P
enet
ratio
n
Du
rab
ility
in D
irty
Wa
ter
Abi
lity
to H
andl
e F
reez
ing
Wav
e D
ampi
ng
Wat
er L
evel
Res
pons
e T
ime
Line
arity
and
Hys
tere
sis
Out
put
Sta
bilit
y
Abi
lity
to R
ead
Qui
ckly
Aft
er
Ext
ende
d D
ry P
erio
d
DC
Pow
er
Req
uire
men
t
Long
Te
rm R
elia
bilit
y
List
Pri
ce
Ove
rall
Rat
ing
BUBBLER SENSORS
American Sigma
950 Bubbler 6 7 7 10 Yes 9 9 10 10 10 - 10 9 7 10 8 NA $4,060 8
Campbell Scientific
DB1 Double Bubbler
1 1 1 1 No 5 10 10 10 10 - 1 1* 1 10 5 2 $1,560 1
Digital 12259 Bubbler 9 7 7 10 Yes 8 9 10 10 10 - 5 8 9 10 5 10 $1,200 8
Tesco Reactive Air
System Captive Air 6 7 9 10 Yes 7 7 10 10 10 - 10 9 10 10 1 NA $2,075 8
BelTech BTS BTS 103-
001A Bubbler NA 8 9 - No 1 - - - - - 5 9 6 9 - 10 $995 7
* Error may have been introduced in the RS-232C to 4-20 MA output conversion. ** Increasing the wave damping effect will decrease the water level response time. 10 = excellent; 1 = horrible; NA = not available; A = adjustable, SW = stilling well required; SW? = stilling well recommended; Opt. = optional
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -28-
BelTech BTS Bubbler
(727) 397-1805 http://www.beltechsystems.com General. The BelTech BTS 103-001A was selected for testing. The Bubbler Level Monitor is designed for reliable operation in rigorous environments such as wastewater lift stations, lakes, irrigation, aquifers, and creek level monitoring. Its alternating dual compressor design ensures long life and provides redundancy; the unit will operate with only one working compressor. It operates by blowing air down the attached tube every 52 seconds and measuring the head of liquid with a high-performance pressure transducer. For this particular setup a compressor cycle of seven seconds was used.
Figure 31. BelTech BTX Bubbler Test Results: Overall the BelTech BTS bubbler earned a low rating in comparison to other sensors (7 on a 10-point scale), mostly due to its instability during the air temperature test (as seen in Figure 32). From the results of the six tests run it was apparent the BelTech BTS bubbler does not have tight resolution. At the beginning of the tests a certain range was selected to calibrate the sensor. Depending on the magnitude of the range, the bubbler can only output water levels in certain increments. Therefore, the results showed jumping around in the sensor readings. The graphs in Figures 32 and 34 show examples of the resolution problem. In addition, the BelTech earned a six in the output stability category because its readings were much higher than the actual water level, and they bounced around considerably in the first 80 minutes. However, after that the readings leveled out and became unnoticeable during the long-term trending test, which measured the sensor for 48 hours (Figure 33). This accounts for the drastic difference in ratings for output stability and long-term reliability.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -29-
Table 9. Evaluation ratings for BelTech BTS Bubbler
Sen
sor
Bra
nd a
nd
Mod
el
Sim
plic
ity a
nd
Cor
rect
ness
of
Inst
ruct
ions
Eas
e of
Ins
talla
tion
Eas
e of
Cal
ibra
tion
Per
form
ance
Dur
ing
Flu
ctua
ting
Air
Tem
pera
ture
Wat
er L
evel
R
esp
onse
Tim
e
Lin
earit
y an
d H
yste
resi
s
Out
put S
tabi
lity
Abi
lity
to R
ead
Qui
ckly
A
fter
Ext
ende
d D
ry
Per
iod
Lon
g T
erm
Rel
iabi
lity
Ove
rall
Rat
ing
BelTech BTS 103-001A
NA 8 9 1 5 9 6 9 10 7
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -30-
Air Temperature Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00
Time (hours)
Sen
sor
Ou
tpu
t (i
nch
es)
0
10
20
30
40
50
60
Air
Tem
per
atu
re (
C)
BelTech
Air Temperature
Figure 32. BelTech BTS temperature test
Long-Term Reliability
10
11
12
13
14
15
16
17
18
19
20
8/9/2002 0:00 8/9/200212:00
8/10/20020:00
8/10/200212:00
8/11/20020:00
8/11/200212:00
8/12/20020:00
8/12/200212:00
8/13/20020:00
Time
De
pth
(in
ch
es
)
Druck (control)
BelTech
Figure 33. BelTech BTS long-term test
BelTech Drying Effects
17.5
17.6
17.7
17.8
17.9
18
18.1
18.2
18.3
18.4
18.5
0 50 100 150 200 250 300 350 400
Time (minutes)
Wat
er
Le
ve
l (i
nc
he
s)
BelTech
Druck (control)Dry for 5 days
Figure 34. BelTech BTS drying test
BelTech Time Lag Test
0
5
10
15
20
25
10/16/200117:25
10/16/200117:28
10/16/200117:31
10/16/200117:34
10/16/200117:36
10/16/200117:39
10/16/200117:42
10/16/200117:45
10/16/200117:48
Time
De
pth
(in
ch
es
)
BelTech
Druck (control)
Figure 35. BelTech BTS time lag test
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -31-
SUMMARY AND CONCLUSIONS
This set of tests was conducted as a continuation to the report developed by ITRC in February of 1999. The results (ratings) in this portion of the study were determined by a comparison of all sensors, including those previously tested by ITRC. A quick and easy procedure has been developed to test the performance of water level sensors. Therefore, additions and updates may be continually incorporated into the study. The continuous testing method developed by ITRC has become a way for irrigation districts and farmers to select the appropriate sensors for their individual needs. As part of the selection process, the sensors were broken down into categories based on the operational type (bubbler, float, submersible, ultrasonic), installation requirements, performance, and cost. All sensors tested within each operational type category were compared and rated.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center -32-
REFERENCES
Burt, A.G., M.C. Lehmkuhl, C.M Burt, and S.W. Styles. 1999. Water Level Sensor and Datalogger Testing and Demonstration. Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo, CA. Irrigation Training and Research Center. 2002. SCADA – Supervisory Control and Data Acquisition. Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo, CA. Piao, X. and L. Burt. 2001. Remote Monitoring and Control – System Set-Up. Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo, CA. Yasutake, M. 2002. LOOKOUT Instructions for a Portable SCADA – Creating Object. Irrigation Training and Research Center, California Polytechnic State University, San Luis Obispo, CA.
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
APPENDIX A Contact Information
Water Level Sensor Testing http://www.itrc.org/reports/sensors/testing.pdf ITRC Report No. 04-005
Irrigation Training and Research Center A-1
Company Address Phone Fax Email Web Site
ACR Systems Unit 210, 12960 84th Ave. Surrey, B.C. Canada V3W-1K7
(800) 663-7845 (604) 591-2252 acr@acrsystems.com http://www.acrsystems.com
AGM Electronics P.O. Box 32227 Tucson, AZ 85751-2227
(520) 722-1000 (520) 722-1045 - -
American Sigma P.O. Box 820 Medina, NY 14103-0820
(800) 635-4567 (716) 798-5599 sigma@americansigma.com http://www.americansigma.com
Automata 10551 E. Bennett Road Grass Valley, CA 95945-7806
(800) 994-0380 (530) 273-0381 automata@automata-inc.com http://www.automata-inc.com
Badger Meter P.O. Box 581390 Tulsa, OK 74158
(918) 836-8411 (918) 832-9962 jzimmer@badgermeter.com http://www.badgermeter.com
Bailey-Fischer & Porter 125 East County Line Road Warminster, PA 18974
(215) 674-6000 (215) 674-6740 Webmaster@bailey.com http://www.ebpa.com
BelTech BTS Systems Inc.
13000 98th Ave. N Seminole, FL. 33776
(727) 397-1805 (727) 595-4387 donald.parker@beltechsystems.com http://www.beltechsystems.com
Campbell Scientific 815 West 1800 North Logan, UT 84321
(435) 753-2342 (435) 750-9540 info@campbellsci.com http://www.campbellsci.com
Celesco PT1MA Transducer Products
7800 Deering Avenue Canoga Park, CA 91309
(800) 423-5483 (818) 340-1175 On website http://www.Celesco PT1MA.com
Coastal Environmental Systems
820 First Avenue South Seattle, WA 98134
(800) 488-8291 (206) 682-5658 pkelly@coastal.org http://www.coastalenvironmental.com
Digital Control Corporation
10871 75th St. North Largo, FL 33777 (800) 335-5219 (727)547-1722 dcc@gte.net http://www.digitalcc.com
Druck 1230 4 Dunham Drive New Fairfield, CT 06812
(203) 746-0400 (203) 746-2494 sales@Druck 1230inc.com http://www.Druck 1230.com/usa
Dryden Instrumentation
6436 Homer Drive Anchorage, Alaska 99518
(907) 344-4995 (907) 344-8013 - -
Endress + Hauser P.O. Box 246 Greenwood, IN 46142-0246
(888) ENDRESS (317) 535-8498 On website http://www.us.endress.com
Global Water 11257 Coloma Road Gold River, CA 95670 (800) 876-1172 (916) 638-3270 globalw@globalw.com http://www.globalw.com
Instrumentation Northwest
14972 NE 31st Circle Redmond, WA 98052
(800) 776-9355 (425) 867-0404 info@inwusa.com http://www.inwusa.com
Intermountain Environmental
601 West 1700 South, Suite B Logan, UT 84321-6219
(800) 948-6236 (435) 755-0794 info@inmtn.com http://www.inmtn.com
Keller 46W 3303 Airline Blvd., Suite B Portsmouth, VA. 23701
(877) 2-KELLER 46W
(757) 465-7680 On web site http://www.Keller 46W-Druck 1230.com
KPSI 34 Research Drive Hampton, VA 23666
(800) 328-3665 (757) 865-8744 kpsi@cts.com http://www.kpsi.com
Lundahl Instruments 429 South Main Logan, UT 84321
(888) 525-7300 (801)753-7490 solution@lundahl.com http://www.lundahl.com
Milltronics 709 Stadium Drive Arlington, TX 76011
(817) 277-3543 (817) 277-3894 raulc@milltronics.com http://www.milltronics.com
Stevens Water Monitoring Systems
P.O. Box 688 Beaverton, OR 97075-0688
(800) 452-5272 (503) 469-8100 info@stevenswater.com http://www.stevenswater.com
Tesco Controls 3434 52nd Avenue Sacramento, CA 95823
(916) 395-8800 (916) 394-1893 - -
top related